DE112020007163T5 - Numerical control and numerical control method - Google Patents

Abstract

A numerical controller that performs control to vibrate a tool and a workpiece relative to each other includes: a spindle processing unit for detecting a change in spindle speed; a phase difference calculation unit for calculating a phase difference, which is a time lag of a vibration backward position relative to a vibration forward position; and a vibration amplitude calculation unit for calculating a vibration amplitude which is a difference between the vibration forward position and the vibration backward position. When the spindle processing unit detects a change in spindle speed during execution of a command block, the phase difference calculation unit recalculates the phase difference to suppress the vibration amplitude from changing due to the change in spindle speed, and the vibration amplitude calculation unit changes the vibration amplitude based on the recalculated phase difference .

Description

technical field

The present disclosure relates to a numerical controller and a numerical control method.

Technical background

There is a method in which, when a workpiece is machined by a machine tool, chips are broken by vibrating the cutting tool and the workpiece in the machining feed direction relative to each other. A numerical controller disclosed in Patent Document 1 includes a device for calculating, as a phase difference, the time delay of a vibration return position relative to a vibration advance position, which is determined based on a command block in a machining program from a relationship between the vibration amplitude and the feed speed of the tool relative at the time of movement to the workpiece, and to generate, based on the phase difference, the vibration advance position and the vibration return position as a movement trajectory for each driving axis.

Prior Art Document

patent document

Patent Document 1: Japanese Patent No. 5745710

Brief description of the invention

Technical problem

However, in the technique described in Patent Document 1, the phase difference between the vibration reverse position and the vibration forward position is generated for each command block. If the spindle speed for vibratory cutting changes during the execution of a command block (for example, if the command percentage value is changed during constant surface speed control or spindle override), the phase difference error caused by the change cannot be corrected. This leads to improper setting of vibration conditions, resulting in insufficient chip breaking and excessive stress on machine tool parts (ball screws, etc.), servo motors, and cutting tools.

An object of the present disclosure is to provide a numerical controller and a numerical control method which, even when the spindle speed changes, enables dynamic response of the vibration conditions in vibration cutting to the change, prevents chip breaking failure, and thus enables machining in a wide range of Allow conditions within the load that the machine tool and cutting tool can withstand.

solution to the problem

In order to solve the above problem, according to the present disclosure, a numerical controller that performs control to vibrate a tool and a workpiece relative to each other includes; a spindle processing unit to detect a change in spindle speed; a phase difference calculation unit for calculating a phase difference, which is the time lag of a vibration backward position relative to a vibration forward position; and a vibration amplitude calculation unit for calculating a vibration amplitude which is the difference between the vibration forward position and the vibration backward position. When the spindle processing unit detects a change in spindle speed during execution of a command block, the phase difference calculation unit recalculates the phase difference to suppress a change in vibration amplitude due to the change in spindle speed, the vibration amplitude calculation unit changing the vibration amplitude based on the recalculated phase difference becomes.

Advantageous Effects of the Invention

Numerical control according to the present disclosure enables dynamic response of the vibration conditions of vibration cutting to the change even when the spindle speed changes, prevents failure related to chip breaking, and thus enables machining in a wide range of conditions within the load imposed on the machine tool and can withstand the cutting tool.

character list

• 1 12 is a block diagram showing an example of the configuration of a numerical controller according to Embodiment 1.
• 2 12 is a diagram schematically showing the axis configuration of a machine tool according to Embodiment 1. FIG.
• 3 shows an example of a machining program according to embodiment 1.
• 4 FIG. 12 is a diagram showing an example of a vibration waveform calculated by an interpolation processing unit according to Embodiment 1. FIG.
• 5 14 is a diagram schematically showing the relationship between a vibration advance position R1 and a vibration return position R2 according to Embodiment 1. FIG.
• 6 Fig. 12 is a diagram showing an example of a vibration waveform calculated by a prior art interpolation processing unit.
• 7 FIG. 14 is a flowchart showing a method for resetting the vibration conditions according to Embodiment 1. FIG.
• 8th 12 is a block diagram showing an example of the configuration of a numerical controller according to Embodiment 2.
• 9 12 is a diagram schematically showing the axis configuration of a machine tool according to Embodiment 2. FIG.
• 10 12 is a diagram schematically showing changes in the number of vibrations according to Embodiment 2. FIG.
• 11 FIG. 14 is a flowchart showing a method for resetting the vibration conditions according to Embodiment 2. FIG.
• 12 12 is a diagram showing the relationship between the moving distance along a feed axis and a vibration waveform according to Embodiment 3.
• 13 FIG. 12 is a flowchart explaining a method for resetting the vibration conditions according to Embodiment 3. FIG.
• 14 12 shows an example of the hardware configuration of a control and calculation unit according to Embodiments 1 to 3.
• 15 12 shows an example of the hardware configuration of a control and calculation unit according to Embodiments 1 to 3.

Description of Embodiments

Embodiments of the present disclosure are described below with reference to the attached figures. In the figures, identical or equivalent parts are given the same symbol. Duplicate explanations are simplified or omitted as appropriate. It is noted that the present disclosure is not limited by the embodiments described below. In the figures below, the scale may differ from the actual scale, but this does not limit the content of the present disclosure.

Embodiment 1

1 12 is a block diagram illustrating an example of the configuration of a numerical controller 1 according to the present disclosure. The numerical controller 1 comprises a drive unit 10, an input unit 20, a display unit 30 and a control and calculation unit 40.

The drive unit 10 is a mechanism that drives a workpiece and/or a tool in at least two axial directions. The driving unit has an X-axis servomotor 12 and a Z-axis servomotor 13, which move the workpiece and/or the tool in the X-axis direction and Z-axis direction set for the numerical controller 1. The driving unit has an X-axis servo control unit 15 and a Z-axis servo control unit 16 which position and speed the workpiece and/or the tool in the respective axis directions according to the positions and speeds of the X-axis servo motor 12 and the Control Z-axis servo motor 13 according to. The drive unit includes a spindle motor 11 which rotates a spindle to which the workpiece is fixed, and a spindle servo controller 14 which controls the position of the spindle motor 11 and the rotation of the spindle to which the workpiece is fixed. In the present disclosure, only two axes, the X-axis and the Z-axis, are described by way of example for the sake of simplicity; however, the numerical control is not limited to this and can also control more than three axes or multiple systems (e.g. X1, X2, ...) for each axis.

2 12 is a diagram schematically showing the axis configuration of a machine tool 110 according to Embodiment 1. FIG. The machine tool 110 is controlled by the numerical controller 1 . A tool holder 51 on which a cutting tool 50 of the machine tool 110 is fixed is controlled by the X-axis servomotor 12 and the Z-axis servomotor 13 of the numerical controller 1 so as to move in the X-axis and moved along the Z-axis. The workpiece 60 is fixed to a headstock 70 with the position and rotation of the headstock 70 being controlled by the spindle motor 11 . The workpiece 60 rotates on the headstock 70 about the axis of rotation 71 of the headstock 70.

In 2 the headstock 70 rotates about the axis of rotation 71 while the cutting tool 50 moves along a trajectory 52 to cut a side surface of the workpiece 60 . Incidentally, the trajectory 52 in the figure does not represent vibrations along a feed axis (X-axis or Z-axis). In the following description, in vibration cutting, the vibrations are generated along the feed axis (of the tool). However, this is not a limitation; since the tool and workpiece 60 need only vibrate relative to each other, the spindle can also be vibrated.

The input unit 20 includes input devices such as a keyboard, buttons, and a mouse, and allows a user to input commands, machining programs, parameters, and the like into the numerical controller 1. The display unit 30 includes display devices such as a liquid crystal display, and displays information generated by the controller - and calculation unit 40 have been processed.

The control and calculation unit 40 includes an input control unit 41, a data setting unit 42, a storage unit 43, a display image processing unit 44, an analysis processing unit 45, an interpolation processing unit 46, a spindle processing unit 47, an acceleration/deceleration processing unit 48, and an axis data output unit 49.

The input control unit 41 receives information inputted from the input unit 20 . The data setting unit 42 stores the information received from the input control unit 41 in the storage unit 43. For example, when the input is editing of a machining program 432, the edited contents are reflected in the machining program 432 stored in the storage unit 43; when a parameter is input, it is stored in a parameter storage area 431 in the storage unit 43 .

The storage unit 43 stores information such as the parameters 431 to be used in the processing of the control and calculation unit 40, the machining program 432 to be executed, and screen display data 433 to be displayed on the display unit 30. The storage unit 43 includes a shared area 434 for storing temporarily used data other than the parameters 431 and the machining program 432 . The display image processing unit 44 controls the display unit 30 to display the screen display data stored in the storage unit 43 .

The analysis processing unit 45 includes a movement command analysis unit 451 and a vibration command analysis unit 452. The movement command analysis unit 451 reads the machining program 432 stored in the storage unit 43, which contains one or more command blocks (also simply referred to as blocks), analyzes the read machining program 432 Block by block and generates a motion command in terms of movement, rotation, speed, etc. for the axes contained in the command blocks. The vibration command analysis unit 452 analyzes whether a vibration command is included in the machining program 432; when a vibration command is included, the unit generates vibration conditions such as a vibration frequency and a vibration amplitude included in the vibration command. The interpolation processing unit 46 and the spindle processing unit 47 acquire the movement command and vibration command analyzed by the analysis processing unit 45 .

3 Fig. 12 is a diagram showing an example of a machining program 432. The machining program 432 is read line by line (or block by block); the movement command and the vibration command are analyzed in the analysis processing unit 45; Driving and vibration for each axis are performed in accordance with each command in the interpolation processing unit 46 described later. The blocks of the machining program mean execution of a spindle speed command, positioning, vibration cutting, and turning, respectively. Each block contains a command to be executed. For example, the F command in "G1Z-10.F0.1" specifies the amount of movement along the feed axis (X-axis or Z-axis) per revolution of the spindle. In the case of F0.1, the movement along the feed axis is at a speed of 0.1 mm/rev. Vibration cutting is performed according to the movement command and vibration command included in such command blocks.

The interpolation processing unit 46 includes a phase difference calculation unit 462, a vibration amplitude calculation unit 463, a vibration frequency calculation unit 464, a vibration moving distance calculation unit 465, and a moving distance combining unit 466.

The function of the interpolation processing unit 46 is explained with reference to 4 described. 4 14 is a diagram showing an example of a vibration waveform calculated in the interpolation processing unit 46. FIG. 4(a) shows a representation to illustrate the change in the spindle speed over time. It can be seen that at a certain time t0, vibration cutting starts according to the execution of the command block, and at time t2, the spindle speed increases. Such changes in spindle speed are detected in the spindle processing unit 47 described below and forwarded to the interpolation processing unit 46 .

4(b) Fig. 12 is a diagram showing the relationship between the vibration forward position R1 and the vibration return position R2. The vertical axis represents the distance of travel along the feed axis (X-axis or Z-axis). The vibratory return position R2 begins its movement with a time lag of t1 - t0 relative to the vibratory advance position R1. The phase difference calculation unit 462 calculates phase differences (W and W in the figure) each corresponding to the time delay from t1 - t0 of the vibration return position R2 relative to the vibration advance position R1. The phase difference calculation unit 462 recalculates the phase difference W as described later according to a change in the spindle speed during execution of the command block. Two types of trajectories, ie, the vibration advance position R1 and the vibration return position R2, are prepared using the phase difference calculated based on the vibration conditions and the machining conditions.

The vibration amplitude calculation unit 463 calculates the vibration amplitude, which is the difference between the moving distance of the vibration forward position R1 and that of the vibration reverse position R2, at each time point from the start to the end of the command block. 4(c) shows the change in vibration amplitude over time during the period in which the process starts at time t0 and ends at time t4.

The vibration frequency calculation unit 464 calculates the vibration frequency from the number of vibrations per spindle revolution and the spindle speed. 5 Fig. 12 is a diagram schematically showing the relationship between the vibration advance position R1 and the vibration return position R2. The reference character R3 of 5 denotes a trajectory along one of the feed axes (X-axis or Z-axis); the straight line connecting the maximum positions of the trajectory R3 is the vibration advance position R1, and the straight line connecting the minimum positions thereof is the vibration return position R2. The figure shows the relationships between the vibration amplitude A, which is the difference between the vibration advance position R1 and the vibration return position R2, the feed amount F along the feed axis per spindle revolution, and the required time T per spindle revolution. As in 5 , a vibration frequency of 350 Hz is calculated when the number of vibrations per spindle revolution is 3.5 and the spindle speed is 6000 rpm.

The vibration moving distance calculation unit 465 calculates a vibration moving distance which is the difference between the vibration forward position R1 and the vibration backward position R2 multiplied by the vibration waveform at each time ( 4 (d) ). The moving distance combining unit 466 calculates a combined moving distance by combining the command moving distance and the vibration moving distance analyzed for each block ( 4(e) ).

The spindle processing unit 47 includes a spindle rotation command generation unit 471 and a spindle rotation speed calculation unit 472. The spindle rotation command generation unit 471 calculates a rotation speed to be instructed to the spindle motor 11 in accordance with the machining program 432, and outputs a rotation speed command to the axis data output unit 49. The spindle speed calculation unit 472 obtains the phase of the spindle motor 11 from a detector (not shown) such as an encoder attached to the spindle motor 11 and calculates the spindle speed. Alternatively, the spindle speed can be calculated based on signals returned from the spindle servo controller 14 . The spindle processing unit 47 monitors the spindle speed during execution of the instruction block to detect changes in spindle speed. For example, the continuous calculation of spindle speed by spindle speed calculation unit 472 during execution of the instruction block allows spindle processing unit 47 to detect changes in spindle speed. The spindle processing unit 47 continuously sends the continuously calculated spindle speed to the interpolation processing unit 46.

The acceleration/deceleration processing unit 48 converts the combined movement distance for each drive axis, which is output from the interpolation processing unit 46, into a movement command per unit time that performs acceleration and deceleration in accordance with a predetermined acceleration movement/delay pattern included. The axis data output unit 49 outputs, to each axis of the drive unit 10 , a spindle rotation command and the movement command and vibration command for the feed axis processed by the acceleration/deceleration processing unit 48 .

The reason why the phase difference W is recalculated will now be explained. A vibration amplitude-feed ratio Q defined in the machining program 432 is the ratio of the vibration amplitude A to the feed amount per spindle revolution F, and is expressed by the following equation (1). $$\text{Q}=\text{A/F}$$

$$\text{W}=\text{AT/F}=\text{QT}$$

It is assumed that the time required per spindle rotation is T. Then, the phase difference W, the vibration amplitude A and the feed amount F per spindle revolution have the relationship according to the following Equation (2), where Equation (3) is derived via the phase difference W from Equations (1) and (2). $$\text{A}/\text{W}=\text{F/T}$$

$$\text{W}=\text{AT/F}=\text{QT}$$

Equation (3) shows that the phase difference W increases or decreases depending on the time T per spindle revolution when the time T per spindle revolution changes with a change in spindle speed during the execution of a block.

6 Fig. 12 is a diagram showing an example of a vibration waveform calculated by a prior art interpolation processing unit. In 4 the phase difference W is recalculated with respect to an increase in spindle speed, in 6 however, the phase difference W is fixed, as in 6(b) is shown. During the execution of the command block, if the spindle speed increases by changing the percentage command value by constant surface speed control or spindle override, and the phase difference W is kept constant under the vibration condition specified in the command block, after changing the spindle speed, the vibration amplitude, that is, the difference, increases between the vibration forward position R1 and the vibration return position R2 as shown in FIGS 6(c) until 6(e) is shown. Such fluctuations can result in excessive amplitude on machine tool components, etc. On the other hand, if the phase difference W remains constant when the spindle speed is slowed down, the vibration amplitude is not enough to break the chips, which may result in poor machining.

In contrast, in 4 recalculates the phase difference W' after the spindle speed change to suppress the vibration amplitude from fluctuating in response to the spindle speed change during the execution of the command block. Based on the recalculated phase difference W', the trajectory of the vibration return position R2 is adjusted to avoid fluctuation of the vibration amplitude. In this way, interference caused by excessive or insufficient vibration amplitude can be eliminated.

In practice, the vibration amplitude component goes through a position loop gain before the servo motor is driven. Because the position loop gain acts as a low-pass filter, amplitude roll-off occurs as the vibration frequency of the feed axis increases. Therefore, according to another preferred configuration, the vibration frequency calculation unit 464 calculates the amplitude attenuation based on the vibration frequency. When the vibration amplitude is changed based on the recalculated phase difference, the vibration amplitude calculation unit 463 changes the vibration amplitude to suppress the amplitude damping. In this way, the damping of vibration amplitude with respect to the increase or decrease in vibration frequency caused by changes in spindle speed can be weakened, thereby eliminating problems caused by excessive or insufficient vibration amplitude. Such vibration damping suppression can be combined with the embodiments described below.

The procedure for resetting the vibration conditions in embodiment 1 will be explained with reference to the flow chart of FIG 7 described. The procedure of the flowchart represents a numerical control method of the numerical controller 1 according to the present disclosure.

In step S101, a command block included in the machining program 432 is executed, and the vibration conditions are set. In step S102, spindle rotation and machining are started. In step S103, the spindle processing unit 47 detects whether or not there is a change in spindle speed. When a change in spindle speed is detected, the procedure advances to step S105. If there is no change in spindle speed, the vibration conditions defined in the command block are maintained in step S104. Calculated in step S105 the phase difference calculation unit 462 resets the phase difference W in order to suppress the vibration amplitude A from fluctuating after the spindle speed is changed. Ideally, in order to suppress the fluctuation of the vibration amplitude A, the vibration amplitude A is constant before and after the spindle speed is changed during the execution of the command block. However, a perfectly constant value is not required. Fluctuations due to various factors in actual machining, such as the computing power of the control and calculation unit 40, the machining program 432, etc. are allowed. In step S106, the vibration amplitude calculation unit 463 adjusts the trajectory of the vibration return position R2 based on the recalculated phase difference W, whereby the vibration amplitude A changes.

In step S107, it is determined whether the execution of the command block has ended. If the execution of the command block has not yet ended, the procedure returns to the point before step S103 and the spindle speed monitoring is repeated. When the command block finishes executing, the procedure ends.

As described above, the numerical controller 1 according to Embodiment 1 is a numerical controller that performs control to vibrate the tool and the workpiece 60 relative to each other. The numerical controller 1 includes: the spindle processing unit 47 that detects a change in spindle speed; the phase difference calculation unit 462 which calculates a phase difference which is the time delay of the vibration return position relative to the vibration advance position; and the vibration amplitude calculation unit 463 which calculates the vibration amplitude from the difference in moving distance between the vibration forward position and the vibration backward position. When the spindle processing unit 47 detects a change in the spindle speed during execution of the command block of the machining program, the phase difference calculation unit 462 recalculates the phase difference to suppress a change in the vibration amplitude due to the change in the spindle speed, the vibration amplitude calculation unit 463 calculating the vibration amplitude based on of the newly calculated phase difference changes. This configuration enables dynamic response of the vibration conditions of vibration cutting to the change even when the spindle speed changes, prevents chip breaking failure, and thus enables machining in a wide range of conditions within the load that the machine tool and cutting tool can withstand.

Embodiment 2

The numerical controller 1 according to Embodiment 2 further includes a vibration number changing unit 461. 8th is intended to describe the numerical controller 1 according to Embodiment 2, but the description of the configuration of units that are the same as those of Embodiment 1 will be omitted.

As described in Embodiment 1, the vibration frequency in vibration cutting is calculated from the spindle speed and the number of vibrations per spindle revolution. In addition, if the spindle speed increases during the execution of a command block, the vibration frequency becomes too high, which can cause undue stress on machine tool components (eg, ball screws), servo motors, and cutting tools. Therefore, the number of vibrations changing unit 461 dynamically changes the number of vibrations per spindle rotation in response to changes in spindle speed during execution of a command block.

9 12 is a diagram schematically showing the axis configuration of a machine tool 110 according to Embodiment 2. FIG. The figure shows an example of face machining with constant surface velocity control on a workpiece 60. As headstock 70 rotates about pivot axis 71, cutting tool 50 moves along trajectory 53 to machine the face of workpiece 60. In constant cutting speed control, the spindle speed is controlled so that the peripheral speed is constant with respect to changes along the X-axis. The smaller the machining radius during execution of the command block (ie, the closer the X coordinate is to the center), the faster the spindle speed becomes, with the vibration frequency increasing in proportion to the spindle speed. It is noted that face machining with constant surface speed control is an example in which the vibration frequency varies during execution of the command block, and the present disclosure is not limited to this control.

The vibration number changing unit 461 compares the vibration frequency calculated by the vibration frequency calculation unit 464 with a set threshold value of the vibration frequency. The vibration frequency calculation unit 464 continuously calculates the vibration frequency lich during the execution of a command block, the vibration number changing unit 461 monitors the changes in the vibration frequency. When the calculated vibration frequency is outside the vibration frequency range determined by the threshold value, the vibration number changing unit 461 changes the currently set number of vibrations per spindle revolution and controls the machine tool 110 to operate within the vibration frequency range.

10 shows schematically the change in the number of vibrations. 10 (a) 12 shows a situation where the coordinate of the X-axis, which is the feed axis, decreases from 50 to 0 over time, with the cutting tool 50 moving along the trajectory 53 toward the rotary axis 71 to machine the workpiece 60 . 10(b) Figure 12 shows the change in spindle speed, revealing that as the X-axis position decreases, the spindle speed increases to 4500 rpm and then becomes constant. 10(c) FIG. 12 shows the number of vibrations per spindle revolution set by the vibration number changing unit 461. FIG. 10(d) FIG. 12 shows the vibration frequency calculated by the vibration frequency calculation unit 464. FIG.

Effective chip breaking in vibratory cutting requires that the number of vibrations per spindle revolution is not a natural number, with the ideal number of vibrations being expressed using n as n + 0.5 (n=0, 1, 2...). . Here, n is 0 or a natural number. Efficient chip breaking means that the chips are broken up into shorter chips on average, rather than into chips of different lengths. A variation of n + 0.5 will result in some variation in chip length, but a variation is acceptable if it does not significantly affect machining. The occurrence of chip breaking failure or a variation in chip length of, for example, ±50% or more is considered to be a significant effect on machining.

In 10(c) is set to 3.5 as an example of the initial value of the number of vibrations set by the machining program 432. 10(d) shows an example of a vibration frequency threshold set to 100 Hz. The set vibration frequency threshold is stored in the storage unit 43 as a parameter 431 . The vibration frequency threshold set as parameter 431 may be dynamically changed in response to feedback regarding the loading of the machine tool or cutting tool.

$$100\left(\text{Hz}\right)\times 60\left(\text{s}\right)/\mathrm{2,5}\left(\text{mal/U}\right)=2400\left(\text{U/min}\right)$$

$$100\left(\text{Hz}\right)\times 60\left(\text{s}\right)/\mathrm{1,5}\left(\text{mal/U}\right)=4000\left(\text{U/min}\right)$$

$$100\left(\text{Hz}\right)\times 60\left(\text{s}\right)/\mathrm{0,5}\left(\text{mal/U}\right)=12000\left(\text{U/min}\right)$$

If the upper threshold of the vibration frequency is 100 Hz, the spindle speeds allowed for the number of vibrations of 3.5, 2.5, 1.5 and 0.5 per spindle revolution along the feed axis are as follows: $$100\left(\text{Hz}\right)\times 60\left(\text{s}\right)/3.5\left(\text{times/u}\right)=1714\left(\text{rpm}\right)$$

$$100\left(\text{Hz}\right)\times 60\left(\text{s}\right)/2.5\left(\text{times/u}\right)=2400\left(\text{rpm}\right)$$

$$100\left(\text{Hz}\right)\times 60\left(\text{s}\right)/1.5\left(\text{times/u}\right)=4000\left(\text{rpm}\right)$$

$$100\left(\text{Hz}\right)\times 60\left(\text{s}\right)/0.5\left(\text{times/u}\right)=12000\left(\text{rpm}\right)$$

When the cutting tool 50 moves toward 0 with respect to the X-axis coordinate of 50 and the spindle speed increases with constant surface speed control, the vibration frequency exceeds the threshold value of 100 Hz when the initial value of the vibration number is 3.5 and the spindle speed exceeds 1714 rpm . Therefore, the number of vibrations changing unit 461 changes the number of vibrations per spindle revolution from 3.5 to 2.5 during execution of the command block. This controls the calculated vibration frequency to be within the vibration frequency range (100 Hz or less) determined by the threshold. In the above illustration, only the upper threshold for the vibration frequency is specified; however, a lower threshold (e.g. 10 Hz) can also be specified and the calculated vibration frequency can be controlled within the vibration frequency range specified by the thresholds (in this case from the lower threshold of 10 Hz to the upper threshold of 100 Hz). .

The number of vibrations is changed by increasing or decreasing from its initial value using a natural number, where the number of vibrations to be selected is that which brings the vibration frequency within the frequency range determined by the threshold and the difference before and minimized after the change. For example, if the original vibration count is 3.5 and 2.5 does not bring the vibration frequency into the frequency range determined by the threshold, then 1.5 is selected as the next candidate vibration count.

A procedure for resetting the vibration conditions in Embodiment 2 will be described next with reference to the flowchart of FIG 11 described. The procedure of the flowchart shows a numerical control method of the numerical controller 1 according to the present disclosure. With reference to 11 were duplicate descriptions of the same steps as in 7 omitted. Steps S201 to S206 are the same as steps S101 to S106, and step S209 corresponds to S107, so the descriptions thereof are omitted.

In step S207, the vibration number changing unit 461 compares the vibration frequency calculated by the vibration frequency calculation unit 464 with the set vibration frequency threshold to determine whether the calculated vibration frequency is within the vibration frequency range specified by the threshold. If the calculated vibration frequency is within the vibration frequency range, the number of vibrations is not changed and the procedure advances to step S209. On the other hand, if the calculated vibration frequency is out of the range, the procedure advances to step S208, where the number of vibrations is changed so that the calculated vibration frequency is within the vibration frequency range during execution of the command block. The procedure advances to step S209 with the changed vibration conditions.

Resonance may occur in some frequency bands of the vibration frequency range determined by the threshold value due to the mechanical structure of the machine tool or other factors. In such a case, settings to avoid a resonant frequency band in the vibration frequency range should be made as a preferred additional configuration. In step S207, the vibration number changing unit 461 determines whether the calculated vibration frequency is within the vibration frequency range determined by the threshold and whether the calculated vibration frequency is included in the resonance frequency band. If the calculated vibration frequency is within the vibration frequency range but included in the resonant frequency band, the number of vibrations that minimizes the difference before and after the change is selected so that the calculated vibration frequency is within the vibration frequency range and not included in the resonant frequency band.

In step S207, the decision to change the number of vibrations is made based on the vibration frequency threshold, but the chip length can also be used as a criterion for changing the number of vibrations. The chip length L is approximated as follows when the number of vibrations per spindle revolution is K and the machining radius of the workpiece is 60r. $$\text{L}=2\mathrm{\pi }\text{r/K}$$

When machining the end face of the workpiece 60 with the above-described constant surface velocity control, as the cutting tool 50 moves toward 0 with respect to the X-axis coordinate of 50, the chip length becomes smaller due to the reduction in the machining radius r. If the chips get too small, it can clog a chip conveyor or cause other problems.

Therefore, instead of the fixed vibration frequency threshold, the chip length can be used as a criterion for step S207. In this case, a detection device such as a camera is provided to detect the length of the chips generated during cutting. During the execution of the command block, the vibration number changing unit 461 receives chip length information from the detector and compares it with a chip length threshold set as a parameter 431 stored in the storage unit 43 . When the length of the chips produced by cutting is outside the chip length range determined by the threshold value, the procedure advances to step S208, where the vibration number changing unit 461 changes the number of vibrations during execution of the command block. If the length of the chips generated by the cutting is within the chip length range determined by the threshold value, the number of vibrations is not changed and the procedure advances to step S209. In this way, the chip length is controlled to be within the range specified by the threshold, preventing chips from clogging the chip conveyor. In addition, this allows dynamic response to the vibration conditions of vibration cutting, preventing chip breaking failure, thus enabling machining in a wide range of conditions within the load that the machine tool and cutting tool can withstand.

Instead of the threshold value for the vibration frequency or the chip length, a threshold value for the load torque can also be specified. In this case, the vibration number changing unit 461 calculates the actual load torque based on the motor drive current values obtained from the spindle servo controller 14, the X-axis servo controller 15, and the Z-axis servo controller 16 of the drive unit 10 during execution of the command block . In step S<b>207 , the vibration number changing unit 461 compares the calculated load torque with the load torque threshold set as the parameter 431 in the storage unit 43 . If the calculated load torque is outside the load torque range determined by the threshold value, the procedure proceeds to step S208, where the vibration number changing unit 461 changes the vibration number so that the load torque calculated during the execution of the command block is within the load torque range determined by the threshold value. If the calculated load torque is within the load torque range determined by the threshold value, the number of vibrations is not changed and the procedure advances to step S209. This enables dynamic response to the vibration conditions in vibratory cutting, preventing chip breaking failure and thus enabling machining in a wide range of conditions within the load that the machine tool and cutting tool can withstand. Instead of calculating the load torque, a threshold value may be set for the motor drive current value, which is used like the vibration frequency, chip length, and load torque in step S207 to determine the need to change the number of vibrations.

In 11 the number of vibrations changing unit 461 changes the number of vibrations (ie, steps S207 and S208) after steps S205 and S206, but they may be executed simultaneously. After the number of vibrations is changed in steps S207 and S208, the recalculation of the phase difference and the change in the vibration amplitude A can be performed in steps S204 and S205. The parameters 431 monitored by the vibration number changing unit 461 during the execution of the command block in step S207 are, as described above, the vibration frequency, the chip length, the load torque, and the motor drive current value; however, at least one of these must be monitored; the number of vibrations can be changed when the multiple parameters 431 are combined and any parameter falls outside the range allowed by the threshold. For example, when monitoring two parameters, vibration frequency and chip length, if the vibration frequency is within the range specified by the threshold but the chip length is outside the range specified by the threshold, the number of vibrations is changed.

As described above, the numerical controller 1 according to Embodiment 2 further includes the vibration count changing unit 461. The vibration count changing unit 461 compares the vibration frequency calculated by the vibration frequency calculation unit 464 with the set threshold value of the vibration frequency range during execution of the command block. If the calculated vibration frequency is outside the vibration frequency range determined by the threshold value, the number of vibrations is changed so that it falls within the range determined by the threshold value during the execution of the command block. This configuration allows the vibration conditions of vibration cutting to dynamically respond to the change when the spindle speed changes, preventing chip breakage, thus enabling machining in a wide range of conditions within the load that the machine tool and cutting tool can withstand.

Embodiment 3

The numerical controller 1 according to Embodiment 3 is configured so that the vibration amplitude is corrected so that when the number of vibrations changes, there is a portion where no chips are cut.

In Embodiment 2, it has been described that the vibration number changing unit 461 selects the changed vibration number according to the condition that n+0.5 with n (n=0, 1, 2, ...) is satisfied. However, if the number of vibrations to lower the vibration frequency is set to 0.5, but this does not bring the changed vibration frequency into the vibration frequency range determined by the threshold value, then the number of vibrations that satisfies the condition n + 0, 5 fulfilled, not selectable. In such a case, a number of vibrations deviating from the ideal condition n + 0.5 can be chosen, e.g. n + 0.3.

12 Fig. 12 shows the relationship between the moving distance along the feed axis and the vibration waveform. The vertical axis shows the distance of movement along the feed axis (X or Z axis) and the horizontal axis shows the phase of the spindle. The solid line shows the vibration waveform along the feed axis. The dashed line shows the vibration waveform along the feed axis at the previous spindle revolution.

If n+0.5 is selected as the number of vibrations for effective chip breaking in vibration cutting, the phase of the vibration cutting trajectory of the Nth spindle revolution (N is a natural number) is out of phase with the phase of the vibration cutting trajectory of the next (N+1)th spindle revolution, where the vibratory cutting path of the next (N+1)th spindle revolution then partially overlaps the cutting path of the Nth spindle revolution that has been passed. This creates a non-cutting portion where no chips are generated on the vibration cutting path of the (N+1)th spindle rotation, enabling sequential chip breaking machining is. Without on the in 12 Being limited in the case shown, in actual machining the trajectory of the Nth spindle revolution may intersect with that of subsequent revolutions (e.g. N+2), not just the next (N+1)th revolution.

12(a) shows a vibration waveform with the ideal number of vibrations satisfying n + 0.5; the trajectory of the N-th spindle revolution and the trajectory of the (N+1)-th spindle revolution partially overlap, resulting in a non-intersecting portion. In contrast, shows 12(b) a vibration waveform in which the number of vibrations deviates from n + 0.5; no non-cutting portion is generated where the trajectory of the N-th spindle revolution and the trajectory of the (N+1)-th spindle revolution intersect, so that the chip breaking is not fully performed.

Therefore, as in 12(c) as shown, the vibration amplitude is corrected when the number of vibrations deviates from n+0.5 to produce a non-cutting portion. When the vibration number changing unit 461 changes the vibration number to a number that is neither 0.5 plus 0 nor 0.5 plus a natural number, the vibration amplitude calculation unit 463 corrects the vibration amplitude based on the spindle phase and the trajectory of each axis so that a non-intersecting section is created.

13 FIG. 12 is a flowchart showing the procedure for resetting the vibration conditions according to Embodiment 3. FIG. The procedure of the flowchart shows a numerical control method of the numerical controller 1 according to the present disclosure. In 13 are duplicate descriptions of the same steps as in 11 omitted. Steps S301 to S306 are the same as steps S201 to S206, and step S311 corresponds to step S209, so the descriptions thereof are omitted.

In step S307 of 13 it is determined whether the vibration frequency calculated by the vibration frequency calculation unit 464 is within the vibration frequency range determined by the threshold value. As described in Embodiment 2, in addition to the vibration frequency, the chip length, the load torque, and the motor drive current can also be used as parameters for the criteria for changing the number of vibrations.

If the calculated vibration frequency is outside the vibration frequency range determined by the threshold value, in step S307 the procedure proceeds to step S308 in which it is determined whether the change can be made with an ideal number of vibrations n+0.5. If the change is possible, a number of vibrations that satisfies the condition of the number of vibrations of n+0.5 is set in step S309. If the change is not possible, in step S310, the number of vibrations is changed under a condition that does not satisfy n+0.5, and the vibration amplitude A is corrected so that a non-intersecting portion is generated. If a non-cutting portion required for chip breaking is generated even if the number of vibrations is deviated from the ideal value (e.g., n+0.3), only the number of vibrations may be changed in step S310.

In the above-described numerical controller 1 according to Embodiment 3, when the vibration number changing unit 461 changes the vibration number to a number that is neither 0.5 plus 0 nor 0.5 plus a natural number, the vibration amplitude calculation unit 463 corrects the vibration amplitude on basis the spindle phase and the trajectory of each axis so that a non-cutting section is created. This configuration allows vibration conditions in vibration cutting to dynamically respond to the change when the spindle speed changes, preventing chip breaking failure, thus enabling machining in a wide range of conditions within the load that the machine tool and cutting tool can withstand. Efficient cutting is performed even when the number of vibrations deviates from ideal conditions.

The hardware configuration of the control and calculation unit 40 of the numerical controller 1 will be described below. 14 1 shows an example of the hardware configuration of a control and calculation unit 40 according to Embodiments 1 to 3. The control and calculation unit 40 can be implemented by a processor 401 and a memory 402 shown in FIG 14 are shown. The processor 401 is, for example, a CPU (also called a central processing unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor (Digital Signal Processor)) or an LSI (Large Scale Integration) system. The memory 402 is z. a RAM (Random Access Memory) or a ROM (Read Only Memory), etc.

The control and calculation unit 40 is implemented by the processor 401 having a program stored in the memory 402 for executing the operation of the control and calculation unit voltage unit 40 reads and executes. It can also be said that the program causes the computer to carry out the procedures and methods of the control and calculation unit 40 . Memory 402 is also used as temporary storage when processor 401 is executing various processes.

The program to be executed by the processor 401 may be a computer program product that includes a storage medium that is a computer-readable and non-transitory storage medium and contains a plurality of computer-executable instructions for performing the data processing. The program to be executed by the processor 401 causes the computer to execute the variety of instructions to perform the data processing.

As in 15 As shown, the control and calculation unit 40 can be implemented by dedicated hardware (processing circuit 403). This can be, for example, a single circuit, a complex circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), a FPGA (Field-Programmable Gate Array), or a combination thereof. The functions of the control and calculation unit 40 can be implemented in part by dedicated hardware and in part by software or firmware.

The configurations in the above-described embodiments are examples of the content of the present invention, and can be combined with another known technique, and some of the configurations can be omitted or changed as far as not departing from the gist of the present invention.

Reference List

1

Numerical control

10

drive unit

20

input unit

30

display unit

40

Control and calculation unit

11

spindle motor

12

X axis servo motor

13

Z axis servo motor

14

Spindle servo control unit

15

X-axis servo controller

16

Z-axis servo controller

41

input control unit

42

data setting unit

43

storage unit

44

display image processing unit

45

analysis processing unit

46

interpolation processing unit

47

spindle processing unit

48

Acceleration/Deceleration Processing Unit

49

axis data output unit

50

cutting tool

51

tool holder

60

workpiece

70

headstock

71

axis of rotation

401

processor

402

Storage

403

processing circuit

431

parameter

432

editing program

433

screen display data

434

shared area

451

Movement command analysis unit

452

vibration command analysis unit

461

Vibration number change unit

462

phase difference calculation unit

463

Vibration amplitude calculation unit

464

Vibration Frequency Calculation Unit

465

Vibration moving distance calculation unit

466

Movement distance combination unit

471

Spindle rotation command generation unit

472

Spindle speed calculation unit

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• JP 5745710 [0003]

Claims (14)

A numerical controller that performs control to vibrate a tool and a workpiece relative to each other, the numerical controller comprising: a spindle processing unit for detecting a change in spindle speed; a phase difference calculation unit for calculating a phase difference, which is a time lag of a vibration backward position relative to a vibration forward position; and a vibration amplitude calculation unit for calculating a vibration amplitude which is a difference between the vibration forward position and the vibration backward position,wherein when the spindle processing unit detects a change in spindle speed during execution of a block of commands, the phase difference calculation unit recalculates the phase difference, to suppress a change in the vibration amplitude due to the change in the spindle speed, and the vibration amplitude calculation unit changes the vibration amplitude based on the recalculated phase difference. Numerical control after claim 1 , wherein the vibration amplitude calculation unit changes the vibration amplitude by adjusting the trajectory of the vibration return position based on the recalculated phase difference. Numerical control after claim 1 or claim 2 further comprising: a vibration number changing unit for changing the number of vibrations per spindle revolution; and a vibration frequency calculation unit for continuously calculating a vibration frequency from the spindle speed and the number of vibrations per spindle revolution during execution of the command block, wherein the vibration number changing unit compares the vibration frequency calculated by the vibration frequency calculation unit with a predetermined vibration frequency threshold value, and when the calculated vibration frequency is outside a vibration frequency range determined by the threshold value, the vibration number changing unit changes the number of vibrations so that the vibration frequency falls within the range determined by the threshold value during execution of the command block. Numerical control after claim 3 , wherein the vibration number changing unit changes the number of vibrations so that the vibration frequency falls within the vibration frequency range determined by the threshold and the difference before and after the change is minimized. Numerical control after claim 3 or claim 4 , wherein when the calculated vibration frequency is within the vibration frequency range but included in a resonance frequency band, the vibration number changing unit changes the number of vibrations so that the vibration frequency falls within the vibration frequency range and is not included in the resonance frequency band. Numerical control after claim 1 , further comprising a vibration number changing unit for changing the number of vibrations per spindle revolution, wherein when, based on a comparison between the length of chips generated by machining during execution of the command block and a specified chip length threshold value, it is determined that the length of the the machining generated chips is outside the chip length range specified by the threshold value, the vibration number changing unit changes the number of vibrations so that the length of the chips falls within the range specified by the threshold value during execution of the command block. Numerical control after claim 1 further comprising: a vibration number changing unit for changing the number of vibrations per spindle revolution; and a drive unit for driving the workpiece and/or the tool in at least two axial directions, wherein when a comparison is made between a load torque detected by the drive unit during execution of the command block and a specified threshold value of the load torque, it is determined that the load torque obtained from the drive unit load torque is outside the range of load torque specified by the threshold value, the vibration number changing unit changes the number of vibrations so that the load torque falls within the range specified by the threshold value during execution of the command block. Numerical control after claim 1 further comprising: a vibration number changing unit for changing the number of vibrations per spindle revolution; and a drive unit for driving the workpiece and/or the tool in at least two axial directions, wherein when based on a comparison between the Motor drive current value obtained from the drive unit during execution of the command block and a specified threshold value of the motor drive current value, it is determined that the motor drive current value obtained from the drive unit is outside the range of the motor drive current value specified by the threshold value, the vibration number changing unit the number of vibrations so changes so that the motor drive current value falls within the range determined by the threshold value during execution of the command block. Numerical control according to one of claims 3 until 8th , wherein the vibration number changing unit changes the number of vibrations to a number that is 0.5 plus 0 or 0.5 plus a natural number. Numerical control according to one of claims 3 until 9 , wherein when the vibration number changing unit changes the number of vibrations to a number that is neither 0.5 plus 0 nor 0.5 plus a natural number, the vibration amplitude calculation unit changes the vibration amplitude based on a spindle phase and a moving trajectory of each axis so corrected that a non-cutting portion necessary for chip breaking is generated. Numerical control according to one of Claims 1 until 10 , A vibration frequency calculation unit for calculating a vibration frequency from the spindle speed and the number of vibrations per spindle revolution during the execution of the command block, wherein the vibration frequency calculation unit calculates an amplitude damping based on the vibration frequency, and when the vibration amplitude based on the recalculated phase difference is changed, the vibration amplitude calculation unit changes the vibration amplitude to suppress the amplitude damping. A numerical control method for performing control to vibrate a tool and a workpiece relative to each other, the numerical control method comprising: a step of detecting a change in spindle speed during execution of a command block; a step of recalculating a phase difference for suppressing a vibration amplitude change due to the change in spindle speed; and a step of changing the vibration amplitude based on the recalculated phase difference. Numerical control methods claim 12 further comprising: a step of monitoring at least one of parameters obtained during execution of the command block, the parameters being vibration frequency, load torque, motor drive current value, and length of chips generated by machining; a step of comparing one of the monitored parameters to a threshold set for the parameter; and a step of, if the parameter is outside an allowable range of the parameter determined by the threshold, changing the number of vibrations during execution of the command block so that the monitored parameter falls within the range determined by the threshold. Numerical control method Claim 13 further comprising: a step of determining, based on the spindle phase and the trajectory of each axis, whether a non-cutting portion required for chip breaking is generated when the number of vibrations is changed during execution of the command block; and a step of correcting the vibration amplitude so that the non-cutting portion is generated when the non-cutting portion required for chip breaking has not been generated.

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